从SQL表中获取以前的记录

Question

I figure out how I can get the next adid using this:

$sql_next = "SELECT adid FROM table WHERE adid > $current_adid ORDER BY adid 
LIMIT 1";
if ($result = $mysqli->query($query)) {
while ($row = $result->fetch_assoc()) {

$next = $row['adid'];

echo '<a href="https://someurl.com/'.$next.'">Next</a>';

}
}

However, I am not sure how to get the previous adid. I tried changing WHERE adid < $current_adid but it didn't do the trick. What should I use to get a previous record from the SQL table?

Answer 1

You need to reverse more than just the comparison:

SELECT adid
FROM table
WHERE adid < $current_adid
ORDER BY adid DESC
LIMIT 1;

The ORDER BY direction also needs to be reversed.

You could also replace these with:

SELECT MIN(adid)
FROM table
WHERE adid > $current_adid;

SELECT MAX(adid)
FROM table
WHERE adid < $current_adid;

The aggregation functions might make the logic clearer.